[CarGuys]

Brake Fluid should be checked for level and more important contamination from water and other corrosive actions. Except for DOT 5 , DOT 3 and 4 Brake fluids are Hydroscopic and absorb mositure. They also degrade from the interaction of metal particles in the internal brake system.

That said they are two schools-

Old school where the brake fluid is topped of at every oil change. Not a good idea!

New school ( Also manufactures recommendations ) where the fluid level is checked and also tested. If low the customer is notified that there are two possible reasons for this.

One- A leak

Two- The brake pads are wearing down getting thin and the brake caliper pistons are moving out. This lowers the fluid and at the same time notifies the consumer that brake pad wear is advancing.

If contaminated a fluid flush is recommended.